1. Field of the Invention
The present invention relates to an apparatus for subjecting a target object to a plasma process in a semiconductor processing system by using a plasma and, more particularly, to an inductively coupled type dry etching apparatus whose process chamber is divided into a plasma generating space and a processing space by an intermediate electrode. Note that semiconductor processing means various types of processing operations performed to manufacture, on a target object, e.g., a semiconductor wafer or an LCD substrate, semiconductor devices and structures including wiring layers and electrodes to be connected to the semiconductor devices by forming semiconductor layers, insulating layers, conductive layers, and the like on the target object with predetermined patterns.
2. Discussion of the Background
As a plasma processing apparatus used in semiconductor processing systems, there is an inductively coupled type dry etching apparatus. This dry etching apparatus generally has a process chamber with a ceiling of a dielectric wall, on which an annular or spiral RF (radio-frequency) antenna is disposed. Further, there is an apparatus of this type having a triode structure, in which the interior of its airtight process chamber is divided into a plasma generating space and a processing space by an intermediate electrode, such as grid. In the etching apparatus having the triode structure, a process is performed as follows.
First, a target object is placed on a lower electrode arranged in the processing space. Subsequently, the process chamber is exhausted by an exhaust system connected to the processing space, thereby setting the entire interior of the process chamber to a predetermined pressure-reduced atmosphere. While the process chamber is continuously exhausted, a process gas is supplied from a process gas supply system to the plasma generating space.
In this state, a plasma generating RF power is applied to the RF antenna so that the process gas supplied to the plasma generating space is excited and dissociated, thereby generating a high-density plasma.
Simultaneously, a bias RF power is applied to the lower electrode to guide, through the intermediate electrode, an etchant in the plasma onto the surface of the wafer arranged in the processing space. Only a desired etchant in the plasma is introduced into the processing space by the intermediate electrode arranged as described above between the plasma generating space and the processing space, thereby etching the wafer.
The plasma is influenced by the pressure in the process chamber, the RF power applied to the antenna, and the like. For example, the plasma diffuses more in the process chamber when the pressure in the process chamber is lower or the RF power applied to the antenna is larger. On the other hand, the plasma stays closer to the RF antenna when the pressure is higher or the RF power is smaller. Further, planar uniformity of the process on the wafer varies, depending on the mixture ratio of the process gas.
As described above, where the intermediate electrode is arranged in the process chamber to divide it into the plasma generating space and the processing space, a ground surface can be provided to face the wafer. With this arrangement, even if the plasma varies due to fluctuation of various conditions, its influence on the wafer can be minimized.
However, in the inductively coupled type dry etching apparatus having the triode structure, there are drawbacks in that the intermediate electrode is overheated and deformed, and some of the input energy from the antenna is wasted. Where the intermediate electrode is deformed, the distance between the wafer and the intermediate electrode becomes less uniform, thereby lowering planar uniformity of the process on the wafer. Further, where the intermediate electrode is deformed or damaged, the wafer may be also damaged or the interior of the process chamber may be contaminated. Where some of the input energy from the antenna is wasted, the process efficiency is decreased.